1. Field of the Invention
The present invention relates to an apparatus for producing a fasciated yarn. More particularly, it relates to an apparatus of this type comprising two air nozzles, each of which impart a reverse directional twist to a fiber bundle.
2. Description of the Related Art
In a faciated yarn spinning system, a fiber bundle continuously fed from a feed roller of a drafting means is introduced into an air nozzle, in which it is twisted and then detwisted by a vortex whirling therein to form a fasciated yarn. To obtain a strong yarn, it is important in this system to (1) increase the number of free end fibers and (2) entangle the free end fibers firmly around a core portion of the bundle with a larger twisting angle. It is, however, very difficult to carry out the two operations by means of only one air nozzle. That is, in order to increase the number of free end fibers, the twist to be imparted to the fiber bundle must be suppressed so that it does not ascend and reach the vicinity of a nipping point of the feed roller. When, however, a large number of twists is imparted to the fiber bundle so that the free end fibers are firmly entangled around the core portion, the twist cannot be suppressed and tends to ascend until it reaches the vicinity of the nipping point of the feed roller.
To solve this problem, an apparatus is proposed in Japanese Examined Utility Model Publication (kokoku) No. 55-20773, in which as illustrated in FIG. 20, a first air nozzle 32 and a second air nozzle 33, each having a reverse directional twisting function are linearly arranged downstream of a front roller 31 of a drafting means and the first air nozzle 32 is provided at the exit end with a detwisting tube 34. The first air nozzle 32 causes a yarn Y to balloon, by which the yarn Y is placed in forcible contact with the detwisting tube 34. This contact suppresses the twist ascent from the second air nozzle 33 so that it does not reach the vicinity of the nipping point of the front roller 31. The prior art apparatus has a drawback in that, due to the liner arrangement of the two nozzles, the exhaust air from the first air nozzle 32 impinges on the opposing surface of the second air nozzle 33 and causes turbulence, which results in an unstable travel of the yarn Y and disturbance of the function of the second air nozzle 33.
Another prior art apparatus is disclosed in Japanese Examined Patent Publication (kokoku) No. 57-55809, in which as illustrated in FIG. 21, two air nozzles 32, 33, each having a reverse directional twisting function are arranged at an angle, so that the yarn travels through a bend. Although this apparatus solves the above problem of unstable yarn travel caused by the exhaust air from the first air nozzle 32, another drawback is generated. Namely, since the axes of the yarn passages of the two air nozzles 32, 33 intersect at an exit portion of the first nozzle 32, the yarn Y passing through the first air nozzle 32 during the threading operation at the start-up stage travels linearly along the axis of the first air nozzle 32 and thus is difficult to introduce into the second air nozzle 33, which causes problems during start-up. Further, since the yarn passage bends in the vicinity of the exit portion of the first air nozzle 32, the vortex in the first air nozzle is disturbed in this area, and thus the yarn Y is placed in forcible contact with one side of the inner wall; which, in turn, prevents the yarn from obtaining the effect of the vortex within the first air nozzle 32, i.e., the function of the first air nozzle 32 is weakened. Additionally, according to this apparatus, it is difficult to insert a seed yarn, which must be reversely inserted from the exit end of the second air nozzle 33, through the yarn passage of the first air nozzle 32 to the inlet portion of the first air nozzle 32 when yarn piecing.
An apparatus having two air nozzles arranged linearly is disclosed in Japanese Examined Patent Publication (kokoku) No. 56-52133, in which as illustrated in FIG. 22, tow air nozzles 32 and 33 are connected by a connector 35 having a space 35a sectioned by two planes each perpendicular to an axis of a yarn passage, for improving the threading operation from the first air nozzle side to the second air nozzle side at the start up stage. Also, according to this apparatus, since an air stream blown into the second air nozzle 33 from the exit end thereof for reversely inserting a seed yarn is rapidly dispersed, the insertion of the seed yarn is still difficult and, further, fly and foreign matter in the fiber bundle tend to be deposited around the exit end of the first air nozzle 32 and are apt to be irregularly spun into the fiber bundle to form a slub portion in the resultant yarn.